The rate of urinary acidification by the turtle urinary bladder in vitro is coupled to the rate of glucose oxidation. Preliminary studies suggest that the specific pathway of glucose metabolism coupled to the acidification process in this epithelium is the pentose phosphate shunt. Since the major end product of the pentose shunt is NADPH, it is proposed that H ion transport is ultimately coupled in some manner to NADPH oxidation. In this study the quantitative relationship between H ion transport and pentose shunt metabolism will first be determined by simultaneously measuring the transport and metabolic rates by bladders mounted in plastic chambers. Then the effects of specific inhibitors of glucose-6-phosphate dehydrogenase on glycolysis, pentose metabolism, H ion and Na ion transport will be examined. The role of NADPH will be assessed by determining the effects of various electron acceptors on the acidification rate and NADP/NADPH ratio and the effect of varying the acidification rate itself on this ratio. The final objective will be to localize the enzymes of the pentose shunt in the various cell types of the epithelium and define the presence of a NADPH dependent dehydrogenase in the plasma membrane of these cells. These studies should help define the specific energetic requirements for urinary acidification and help develop more rational methods of controlling defects in this process that lead to systemic acid-base disorders.